In the History of Software Patents, this is an important case.  The invention in this case related to seismic prospecting and surveying. Seismic source waves are generated and transmitted downwardly into the earth. There they are deflected by subsurface formations and anomalies. The deflected waves return to the earth’s surface and are detected by transducers, known as geophones, which are distributed on the surface over the area of exploration. The geophones convert the returning mechanical vibrations into electrical signals, which are then recorded on a record medium, such as magnetic tape or chart recorder, for analysis. By studying the records of the deflected waves, analysts are able to make determinations concerning the nature of the subsurface structure of the earth.

In a final rejection, the examiner at the U.S. Patent and Trademark Office stated that the claims were directed to the mathematical procedure outlined in the specification for cross-correlating the sets of signals. He found no reason to distinguish between the method and apparatus claims, holding that distinction to be legally immaterial “Where the only mode of practicing an invention is disclosed by way of an algorithm for use in a computer program.”

The applicant’s main contention was that his claims were not directed to a mathematical procedure but to a method that produces a physical result (the partial product signals) by physical processing of physical signals, all of which are described in mathematical terms, and to apparatus for carrying out special forms of the process.

The U.S. Court of Customs and Patent Appeals stated that the common thread running through prior decisions regarding statutory subject matter is that a principle of nature or a scientific truth (including any mathematical algorithm which expresses such a principle or truth) is not the kind of discovery or invention which the patent laws were designed to protect.

The court also stated that various indicia are helpful in determining whether a claim as a whole calls merely for the solution of a mathematical algorithm. For instance, if the end-product of a claimed invention is a pure number, as in Benson and Flook, the invention is nonstatutory regardless of any post-solution activity which makes it available for use by a person or machine for other purposes. If, however, the claimed invention produces a physical thing, such as the noiseless seismic trace in In re Johnson, the fact that it is represented in numerical form does not render the claim nonstatutory.

With regard to “means for” claims, the court noted that both the examiner and the board of appeals and interferences refused to separately consider appellant’s apparatus claims because the method and apparatus claims were deemed indistinguishable. This problem arises in computer-arts inventions when the structure in apparatus claims is defined only as “means for” performing specified functions. If the functionally-defined disclosed means and their equivalents are so broad that they encompass any and every means for performing the recited functions, the apparatus claim is an attempt to exalt form over substance since the claim is really to the method or series of functions itself. In computer-related inventions, the recited means often perform the function of “number crunching” (solving mathematical algorithms and making calculations). In such cases the burden must be placed on the applicant to demonstrate that the claims are truly drawn to specific apparatus distinct from other apparatus capable of performing the identical functions. The court went on to say that if this burden has not been discharged, the apparatus claim will be treated as if it were drawn to the method or process which encompasses all of the claimed “means” and that the statutory nature of the claim under §101 will then depend on whether the corresponding method is statutory. In this case, the court held that all of appellant’s claims should be treated as method claims because the apparatus claims differ from the method claims only in that the term “means for” has been inserted before each process step to convert the step into the “means” for performing it, wherefore they do not have separate meaning as apparatus claims.

With regard to the method claims, the court stated that correlation or cross-correlation is a mathematical exercise which relates two mathematical functions. It remains a mathematical exercise even when verbally tied to the specific end use of seismic prospecting. Although the claim preambles relate the claimed invention to the art of seismic prospecting, the claims themselves are not drawn to methods of or apparatus for seismic prospecting; they are drawn to improved mathematical methods for interpreting the results of seismic prospecting.